1. Field of the Invention
The present invention generally relates to a circuit capable of improving the performance of a switch mode power supply and amplifier circuit. Specifically, the present invention is a circuit having inductors and diodes disposed between a pair of switches so as to minimize voltage and current transients and maximize efficiency.
2. Description of the Related Art
Dual switch circuits facilitate the sequenced cycling of switches between ON and OFF states to generate a voltage waveform having a square wave pattern. The square wave may be pulse width modulated and filtered to produce a desired waveform.
A common problem inherent to dual switch circuits is that individual switches impede one another, thereby wasting power and producing noise.
For example, FIG. 1 shows a totem pole circuit 1 comprising two electrically connected switches Q1, Q2, examples including FETs, IGBTs, BJTs, HBTs and other semiconductor devices, attached to a voltage source +HV and terminated to ground G2. The totem pole circuit 1 is electrically connected to an exemplary output circuit 3, including an inductor L3, capacitor C1 and ground G1. Operation of the circuit includes switch Q1 being ON when switch Q2 is OFF and switch Q2 being ON when switch Q1 is OFF. As such, the ON state switch Q1 or Q2 must charge the parasitic capacitance of the opposing OFF state switch Q2 or Q1, respectively. Parasitic capacitance is quite high at low voltage states. High transient currents are created through the switches Q1 and Q2, when one is ON and charging the capacitance of the other.
In another example, FIG. 2 shows the addition of two inductors L1 and L2 forming an isolation circuit 4 between switches Q1 and Q2. The isolation circuit 4 dissipates current transients; however, the added inductance causes voltage transients each time switch Q1 or Q2 is turned OFF.
What is required is a circuit capable of sufficiently absorbing transients associated with the function of a switch mode power supply and amplifier circuit, so as to achieve efficient voltage switching and to minimize noise.